i’m not sure what you mean here. LBJ became President on November 22, 1963, so about one year before the 1964 election, and a year and few months before the end of JFK’s term in January 1965. So the two years rule didn’t apply, and he was eligible to run in 1964 and 1968, but opted to not run in 1968 because he didn’t think he could win.